电渗析预处理测定水中溶解性有机氮浓度的研究

Measurements of Dissolved Organic Nitrogen with Electrodialysis Pretreatment

当水样中无机氮(DIN)与总溶解性氮(TDN)质量浓度的比大于0.6时,溶解性有机氮(DON)浓度测定的准确度和标准偏差会受到很大影响。研究了电渗析预处理方式去除水样中部分无机氮离子,对DON浓度测定的影响。结果表明,使用CJM-2型离子交换膜时,并且在对水样适当酸化后溶解性有机碳(DOC)的损失率较小,长江水水样的DOC损失率为5.3%。在最佳工作条下,40 min内对自配水的脱盐率在97%以上。在15 min时,长江水水样中ρ(DIN)/ρ(TDN)<0.6,测定出的DON浓度与没有经过电渗析预处理水样相比更加接近真实值,多次测量值(n=4)的标准偏差分别从18.65%下降到3.25%。

When the DIN/TDN ratio of water sam ple is larger than 0.6, the quantification of dissolved organic nitrogen（DON） will be greatly affected. This paper investigate the accuracy of the DON determination after using the electrodialysis pretreatment to remove the inorganic nitrogen ions. The results show that DOC loss was lower when using the CJM-2 type ion exchange membrane and the DOC loss decreased in the samples after the appropriate acidification. For example, the DOC loss of Yangtze River water sample was 5.3%. At the optimal operating conditions, in 40 minutes, the ratio of desalinization of the synthetic water sample can reach 97%. In 15 minutes, the DIN/TDN ratio of the water sample was less than 0.6, the determination of the concentration of DON when measured with and without electrodialysis pretreatment were compared after electrodialysis, the measured values were closer to the real values, and the standard deviation（n = 4）was decreased from 18.65% to 3.25%.